Most users carry a single mobile device, which is often constrained by battery life and data limitations. These constraints may impede the user experience, as significant data may not be downloaded to the device (e.g., emails) or uploaded from the device (e.g. location signals to improve digital assistance capabilities). Many online services rely on information about a user and/or a user device to provide a service to the user. For example, a traffic notification service needs to know the user's location to provide a commute estimate along with relevant traffic information. An online personal assistant may require calendar information and/or data from email to help the user complete one or more tasks on time. Client devices have enormous amounts of information about the user's activities that could be communicated to the service at any given time. However, the wireless transfer of information uses available battery power and can consume a user's data plan.